The present invention concerns a polycarbonate resin composition containing polycarbonate resin, and more specifically, a polycarbonate resin composition showing outstanding moisture resistance and little decrease in tensile properties.
Polymer alloys composed of a blend of polycarbonate resin (PC) and acrylonitrile-butadiene-styrene (ABS) resin are widely used in applications such as electrical and electronic products and office automation equipment. In recent years, with the increasing requirement for miniaturization and light weight of such products, new molding methods have been attempted, and resins used in such products must increasingly have thin-wall properties, precision molding properties, and high flame retardancy. There has been rapid growth in manufacturing and use in these applications in southeast Asia in recent years. Because of the use and storage of products in high-humidity environments in areas such as southeast Asia, there is frequently a risk of physical deterioration due to low moisture resistance of the resins used.
Generally speaking, polymer alloys containing blends of PC and ABS resin cannot be said to show high moisture resistance. In the case of flame-retardant resin compositions in particular, it is not possible to maintain a high level of moisture resistance.
The present invention provides a flame-retardant resin composition showing moisture resistance which is superior to that of conventional blended alloys of PC and ABS resin.
As a result of thorough research on polycarbonate resin compositions in order to solve the aforementioned problem, the inventors discovered that by using an ABS copolymer in which the alkali metal content of the polycarbonate composition is low and adding an epoxy stabilizer, it is possible to improve moisture resistance, thus arriving at the present invention. Moreover, concerning flame-retardant resin compositions, they discovered that a flame-retardant resin composition showing particularly high moisture resistance compared to conventional compositions could be obtained by using flame retardants in which the acid value of the phosphoric ester was low.
Specifically, the present invention comprises a polycarbonate resin composition containing (A) 1 to 99 parts by weight of polycarbonate resin having a viscosity average molecular weight of 10,000 to 100,000, and (B) 1 to 99 parts by weight of (B-1) a copolymer having as its component parts (a) an aromatic vinyl monomer component, (b) a cyanide vinyl monomer component, and (c) a rubber-like polymer, or (B-2) a copolymer having as its component parts (a) an aromatic vinyl monomer component and (b) a cyanide vinyl monomer component, the aforementioned B-2 being a copolymer having a weight average molecular weight of 30,000 to 200,000 and containing an amount of various alkali metals of 1 ppm or less, and blended in (C) 0 to 40 parts by weight of a phosphoric ester compound with respect to a total of 100 parts by weight of the aforementioned components (A) and (B).
Moreover, by adding to this resin composition 0 to 3 parts by weight of (E) an epoxy stabilizer with respect to a total of 100 parts by weight of the aforementioned components (A) and (B), and as an optional component, 0.01 to 3 parts, preferably 0.05 to about 2, and more preferably from about 0.1 to about 1, by weight of (F) polytetrafluoroethylene with respect to a total of 100 parts by weight of the aforementioned components (A) and (B), a polycarbonate resin composition having even more outstanding moisture resistance can be produced.
The following is an explanation of the various components of the resin composition of the present invention. The polycarbonate resin used in the present invention is an aromatic polycarbonate manufactured by the commonly-known phosgene method or the melt polymerization method (cf. Japanese Unexamined Patent Applications S63-215763 and H2-124934). Examples of the diphenols used as raw materials include 2,2-bis(4-hydroxyphenyl)propane (referred to as bisphenol A); 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane; 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane; 1,1-bis(4-hydroxyphenyl)cyclohexane; 1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclohexane; 1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclohexane; 1,1-bis(4-hydroxyphenyl)decane; 1,4-bis(4-hydroxyphenyl)propane; 1,1-bis(4-hydroxyphenyl)cyclododecane; 1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclododecane; 4,4-dihydroxydiphenyl ether; 4,4-thiodiphenol; 4,4-dihydroxy-3,3-dichlorodiphenyl ether; and 4,4-dihydroxy-2,5-dihydroxydiphenyl ether. Moreover, examples of precursor substances for introducing the carbonate include phosgene and diphenylcarbonate.
In the present invention, the viscosity average molecular weight (Mv) of the polycarbonate resin should be 10,000 or more, preferably 16,000 or more and more preferably 21,000 or more, with a viscosity average molecular weight of 22,000 being particularly preferred. The upper limit of viscosity average molecular weight should be 100,000, and in practice, this limit is usually about 40,000. In the present invention, viscosity average molecular weight was measured based on intrinsic viscosity (limiting viscosity) in methylene chloride at 20xc2x0 C., and it was calculated as follows using the Mark-Houwink viscosity formula:
Limiting viscosity=K(Mv)a 
In the formula, K and a are constants; K=1.23 E-4, a=0.83.
Component (B-1) is a copolymer containing (a) an aromatic vinyl monomer component, (b) a cyanide vinyl monomer component, and (c) a rubber-like polymer.
Examples of (a) the aromatic vinyl monomer include styrene, xcex1-methylstyrene,
o-, m-, or p-methylstyrene, vinyl xylene, monochlorostyrene, dichlorostyrene, monobromostyrene, dibromostyrene, fluorostyrene, p-tert-butylstyrene, ethylstyrene, and vinyl naphthalene, and these substances may be used individually or in combinations of two or more; xcex1-methylstyrene should preferably be used.
Examples of (b) the cyanide vinyl monomer component include acrylonitrile and methacrylonitrile, and these substances may be used individually or in combinations of two or more. There are no particular restrictions on the composition ratio of this component, and this ratio should be selected according to the application in question.
Examples of (c) the rubber-like polymer include polybutadiene, polyisoprene, styrene-butadiene random copolymer and block copolymer, hydrogenates of said block copolymers, diene rubbers such as acrylonitrile-butadiene copolymer and butadiene-isoprene copolymer, ethylene-propylene random copolymer and block copolymer, copolymers of ethylene and xcex1-olefins, ethylene-unsaturated carboxylic acid ester copolymers such as ethylene-methacrylate and ethylene-butylacrylate, acrylate ester-butadiene copolymers, for example, acrylic elastomeric polymers such as butylacrylate-butadiene copolymer, copolymers of ethylene and aliphatic vinyl such as ethylene-vinyl acetate, and ethylene-propylene non-conjugated diene terpolymers such as ethylene-propylene-hexadiene copolymer, butylene-isoprene copolymer, and chlorinated polyethylene, and these substances may be used individually or in combinations of two or more. Preferred rubber-like polymers are ethylene-propylene non-conjugated diene terpolymer, diene rubber, and acrylic elastomeric polymers, with polybutadiene and styrene-butadiene copolymer being particularly preferred.
In addition to the aforementioned components (a), (b), and (c) of component (B), one may also use (d) monomers which are copolymerizable with these components in amounts which do not adversely affect the purpose of the present invention. Examples of such copolymerizable monomers include xcex1,xcex2-unsaturated carboxylic acids such as acrylic acid and methacrylic acid, xcex1,xcex2-unsaturated carboxylic acid esters such as methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, 2-ethyl(meth)acrylate, and 2-ethylhexylmethacrylate; xcex1,xcex2-unsaturated dicarboxylic anhydrides such as maleic anhydride and itaconic anhydride; imide compounds of xcex1,xcex2-unsaturated dicarboxylic acids such as maleimide, N-methylmaleimide, N-ethylmaleimide, N-phenylmaleimide, and N-o-chlorophenylmaleimide, etc., and these monomers may be used individually or in combinations of two or more.
A graft copolymer in which the other components are graft-copolymerized in the presence of (c) a rubber-like polymer is preferred as the copolymer of component (B), with particularly preferred examples being ABS resin (acrylonitrile-butadiene-styrene copolymer), AES resin (acrylonitrile-ethylene-propylene-styrene copolymer), ACS resin (acrylonitrile-chlorinated polyethylene-styrene copolymer), and AAS resin (acrylonitrile-acrylic elastomer-styrene copolymer).
Component (B-2) is a copolymer containing (a) an aromatic vinyl monomer component and (b) a cyanide vinyl monomer component. (B-2) contributes toward improving the moldability (fluidity) of the resin. Examples of (a) the aromatic vinyl monomer component include xcex1-methylstyrene, o-, m-, or p-methylstyrene, vinyl xylene, monochlorostyrene, dichlorostyrene, monobromostyrene, dibromostyrene, fluorostyrene, p-tert-butylstyrene, ethylstyrene, and vinyl naphthalene, and these substances may be used individually or in combinations of two or more, with xcex1-methylstyrene being preferred.
Examples of (b) the cyanide vinyl monomer component include acrylonitrile and methacrylonitrile, and these may be used individually or in combinations of two or more. There are no particular restrictions on the composition ratio thereof, and this ratio should be selected according to the application in question. There are no particular restrictions on the composition ratio of (a) to (b), but the two components should be included in amounts of 95 to 50% by weight of (a) and 5 to 50% by weight of (b) in component (B), with amounts of 92 to 65% by weight of (a) and 8 to 35% by weight of (b) being particularly preferred. A preferred example of the copolymer of component (B) is SAN resin.
In the present invention, the weight average molecular weight (Mw) of component
(B-2) should be 30,000 to 200,000, with a range of 30,000 to 110,000 being preferred.
There are no particular restrictions on the method of manufacturing the copolymer of component (B-2), and any commonly-known method may be used, such as bulk polymerization, solution polymerization, bulk suspension polymerization, suspension polymerization, and emulsion polymerization. Moreover, the individually copolymerized resins may also be blended.
Preferred methods for manufacturing component (B) of the present invention are bulk polymerization, solution polymerization, and bulk suspension polymerization. The alkali metal content of component (B) should be 1 ppm or less, and preferably 0.5 ppm or less, with a content of 0.1 ppm or less being particularly preferred. Moreover, among alkali metals, the content of sodium and potassium in component (B) should be 1 ppm or less, and preferably 0.5 ppm or less, with a content of 0.1 ppm or less being particularly preferred.
Component (C) used in the present invention is a flame retardant, with a specific example being a phosphoric ester compound having the following formula: 
(where R1, R2, R3, and R4 are independent hydrogen atoms or organic groups, excluding the case of R1xe2x95x90R2xe2x95x90R3xe2x95x90R4xe2x95x90H. X denotes an organic group having a valency of 2 or above, p is 0 or 1, q is 1 or a higher integer, preferably less than 30, and r is 0 or a higher integer.
Examples of the organic group in the above formula include an alkyl group, a cycloalkyl group, or an aryl group which may or may not be substituted. In the case of substituted groups, examples of the substituent include an alkyl group, alkoxy group, alkylthio group, halogen, aryl group, aryloxy group, arylthio group, or halogenated aryl group, and groups such as these may be used as substituents in combined groups (such as an arylalkoxy alkyl group) or combined groups in which these substituents are bound by oxygen, sulfur, or nitrogen atoms (such as an arylsulfonyl aryl group). Furthermore, the phrase xe2x80x9can organic group having a valency of 2 or higherxe2x80x9d refers to a group having a valency of 2 or higher created by removing one or more hydrogen atoms bound to carbon atoms from the aforementioned organic groups. Examples include an alkylene group, or preferably a phenylene group, substituted or unsubstituted, and substances derived from polynuclear phenols, such as bisphenols, with the relative position of the free valency of 2 or higher being not critical. Particularly preferred examples include hydroquinone, resorcinol, diphenylol methane, diphenylol dimethylmethane, dihydroxydiphenyl, p,pxe2x80x2-dihydroxydiphenylsulfone, bisphenol A, bisphenol S, and dihydroxynaphthalene.
Specific examples of phosphoric ester compounds include trimethylphosphate, triethylphosphate, tributylphosphate, trioctylphosphate, tributoxyethylphosphate, triphenylphosphate, tricresylphosphate, cresylphenylphosphate, octyldiphenylphosphate, diisopropylphenylphosphate, tris(chloroethyl)phosphate, tris(dichloropropyl)phosphate, tris(chloropropyl)phosphate, bis(2,3-dibromopropyl)-2,3-dichloropropylphosphate, tris(2,3-dibromopropyl)phosphate, bis(chloropropyl)monooctylphosphate, bisphenol A tetraphenyldiphosphate, bisphenol A tetracresyldiphosphate, bisphenol A tetraxylyldiphosphate, hydroquinone tetraphenyldiphosphate, hydroquinone tetracresyldiphosphate, hydroquinone tetraxylyldiphosphate, bisphenol A bisphosphate in which R1-R4 are alkoxy groups such as a methoxy, ethoxy, or propoxy group, and preferably, a (substituted) phenoxy group such as a phenoxy or methyl (substituted) phenoxy group, hydroquinone bisphosphate, resorcinol bisphosphate, and trioxybenzene triphosphate, preferably triphenylphosphate and various bisphosphates.
The aforementioned component (C) is added in cases where flame retardancy is necessary, and the amount added should be 1-40 parts by weight with respect to a total of 100 parts by weight of components (A)+(B), and preferably 3-30 parts by weight, with an amount of 5-20 parts by weight being particularly preferred. If the amount of component (C) is less than the aforementioned range, the effect of the present invention will not be manifested to a sufficient degree, and if it exceeds this range, thermal resistance will be impaired. In the present invention, moreover, it is important that the acid value of the aforementioned phosphoric ester be 1 or less. The acid value of the phosphoric ester should preferably be 0.5 or less, and more preferably, 0.2 or less, and a level of 0.1 or less is particularly preferred, with a level infinitely close to 0 being effective in promoting the hydrolysis resistance of the resin composition of the present invention.
In order to further improve the hydrolysis resistance of the present invention, one may add the epoxy stabilizer of component (E). A preferred epoxy stabilizer is (3xe2x80x2,4xe2x80x2-epoxycyclohexane)methyl 3,4-epoxycyclohexylcarboxylate. This stabilizer may be commercially obtained in the form of R-51 from Asahi Chemical Industries or Celloxide 2021P manufactured by Daicel Chemical Industries. The amount added can be 0.01 to 10 parts by weight with respect to a total of 100 parts by weight of component (A)+(B), with an amount of 0.1 to 0.5 parts by weight being preferred. Moreover, the epoxy stabilizer used is not limited to those blends having the above composition.
Together with the flame retardant, an antidripping agent may also be blended into the resin composition of the present invention. This is component (F), polytetrafluoroethylene. Fluorinated polyolefins which may be used as such an antidripping agent may be commercially obtained or manufactured by a commonly-known method. An example of this is a method in which tetrafluoroethylene is polymerized in an aqueous medium in the presence of a free radical catalyst (such as sodium, potassium, or ammonium peroxydisulfate) at a pressure of 100-1,000 psi and a temperature of 0-200xc2x0 C., and preferably 20-100xc2x0 C. to obtain a white solid. This is presented in detail in the specification of Brubaker""s U.S. Pat. No. 2,393,967.
Although this is not indispensable, it is preferable to use resin having particles with a relatively large diameter, such as an average diameter of 0.3-0.7 mm (chiefly 0.5 mm). This is preferable to ordinary polytetrafluoroethylene powder, which has a particle diameter of 0.05-0.5 mm. The reason why such relatively large-diameter materials are particularly preferred is that they can be easily dispersed in the polymer and show a tendency toward binding of the polymers to one another, resulting in the formation of a fibrous material. The optimum type of this polytetrafluoroethylene is referred to by the ASTM as type 3, and it can be commercially obtained as Teflon 6 (commercial name) manufactured by E.I. Dupont de Nemours and Company. Alternatively, Teflon 30J (commercial name), manufactured by Mitsui Dupont Fluorochemical K.K., may also be commercially obtained. The fluoroolefin can be used in the amount of 0.01 to 1 part by weight, and preferably 0.05 to 1.0 part by weight, with respect to a total of 100 parts by weight of components (A)+(B). In addition, substances such as polysiloxane may be added as flame-retardant and antidripping agents in an amount of 0.1 to 20 parts by weight with respect to a total of 100 parts by weight of components (A) and (B).
Furthermore, in addition to the components mentioned above, other common additives such as pigments, dyes, reinforcing agents (talc, mica, clay, glass fibers, glass flakes, milled glass, carbon fibers, fibrils, silica, glass beads, metal fibers, wollastonite, etc.), colorants (carbon black, titanium oxide, etc.), heat resistance agents, antioxidants, weather-proofing agents (ultraviolet absorbers), lubricants, mold-releasing agents, crystal nucleating agents, plasticizers, fluidity-improving agents, antistatic agents, and inorganic and organic antibacterial agents may be blended in with the heat-resistant resin composition of the present invention during mixing or molding of the resin provided that these do not impair the physical properties of the composition. Specific examples of ultraviolet absorbers, stabilizers, and mold-releasing agents are given below.
Any of the resin compositions of the present invention may contain phosphorus stabilizers as optional components. Any phosphorus stabilizer marketed by a manufacturer of stabilizers, for example, as an antioxidant, may be used. Specific examples include triphenylphosphite, diphenylnonylphosphite, tris(2,4-di-t-butylphenyl)phosphite, trisnonylphenylphosphite, diphenylisooctylphosphite, 2,2xe2x80x2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, diphenylisodecylphosphite, diphenylmono(tridecyl)phosphite, 2,2xe2x80x2-ethylidenebis(4,6-di-t-butylphenol)fluorophosphite, phenyldiisodecylphosphite, phenyldi(tridecyl)phosphite, tris(2-ethylhexyl)phosphite, tris(isodecyl)phosphite, tris(tridecyl)phosphite, dibutylhydrogen phosphite, trilauryltrithiophosphite, tetrakis(2,4-di-t-butylphenyl)-4,4xe2x80x2-biphenylene diphosphite, 4,4xe2x80x2-isopropylidene diphenolalkyl(C12-C15)phosphite, 4,4xe2x80x2-butylidenebis(3-methyl-6-t-butylphenyl)ditridecylphosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, bis(nonylphenyl)pentaerythritol diphosphite, distearyl-pentaerythritol diphosphite, phenyl-bisphenol A pentaerythritol diphosphite, tetraphenyldipropylene glycol diphosphite, 1,1,3-tris(2-methyl-4-di-tridecylphosphite-5-t-butylphenyl)butane, and 3,4,5,6-dibenzo-1,2-oxaphosphane-2-oxide. Examples of commercially-available products include Adekastab PEP-36, PEP-24, PEP-4C, PEP-8 (commercial names, manufactured by Asahi Denka Kogyo), Irgafos 168 (commercial name, manufactured by Ciba-Geigy), Sandstab P-EPQ (commercial name, manufactured by Sandoz), Chelex L (commercial name, manufactured by Sakai Chemical Industry Co.), 3P2S (commercial name, manufactured by Ihara Chemical Industry Co.), Mark 329K, Mark P (commercial names, manufactured by Asahi Denka Kogyo), and Weston 618 (commercial name, manufactured by Sanko Chemical Co.). There are no restrictions on the amount of the phosphorus stabilizer to be added, but it should preferably be added in an amount of 0.0001 to 5 parts by weight with respect to a total of 100 parts by weight of component (A)+(B).
In addition, additives such as hindered phenol antioxidants, epoxy stabilizers, and sulfur stabilizers may also be used. Examples of hindered phenol antioxidants include n-octadecyl-3-(3xe2x80x2,5xe2x80x2-di-t-butyl-4-hydroxyphenyl)propionate, 2,6-di-t-butyl4-hydroxymethylphenol, 2,2xe2x80x2-methylenebis(4-methyl-6-t-butylphenol), and pentaerythritol-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)]propionate. Examples of epoxy stabilizers include epoxidized soybean oil, epoxidized linseed oil, phenyl glycidyl ether, allyl glycidyl ether, and 3,4-epoxycyclohexylmethyl-3xe2x80x2,4xe2x80x2-epoxycyclohexane carboxylate. There are no particular restrictions on the amount of these additives to be used, but they should preferably be added in an amount of 0.0001 to 5 parts by weight with respect to a total of 100 parts by weight of components (A)+(B).
Furthermore, mold-releasing agents may be added in order to improve mold-releasing properties. Examples of preferred mold-releasing agents include silicone mold-releasing agents such as methylphenyl silicone oil and ester or olefin mold-releasing agents such as pentaerythritol tetrastearate, glycerin monostearate, montanic acid wax, and polyalphaolefins. There are no particular restrictions on the amount of these additives to be used, but they should preferably be added in amounts of 0.0001 to 5 parts by weight with respect to a total of 100 parts by weight of components (A)+(B).
Any ultraviolet absorber commonly used in PC resin compositions may be used in the present invention, such as benzotriazole ultraviolet absorbers, benzophenone ultraviolet absorbers, and salicylate ultraviolet absorbers. Examples of benzotriazole ultraviolet absorbers include 2-(2xe2x80x2-hydroxy-5xe2x80x2-methylphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-5xe2x80x2-t-butylphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-5xe2x80x2-t-octylphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-3xe2x80x2,5xe2x80x2-di-t-butylphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-3xe2x80x2,5xe2x80x2-di-amylphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-3xe2x80x2-dodecyl-5xe2x80x2-methylphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-3xe2x80x2,5xe2x80x2-dicumylphenyl)benzotriazole, and 2,2xe2x80x2-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole-2-yl)phenol]. An example of a benzotriazole ultraviolet absorber is UV5411, marketed by American Cyanamid. An example of a benzophenone ultraviolet absorber is UV531, also marketed by American Cyanamid. Examples of salicylate ultraviolet absorbers include phenyl salicylate, p-t-butylphenyl salicylate, and p-octylphenyl salicylate. There are no particular restrictions on the amounts of these additives to be used, but they can preferably be added in amounts of 0.0001 to 5 parts by weight with respect to a total of 100 parts by weight of components (A)+(B).
A compatibilizer may also be added to the thermoplastic resin composition of the present invention. These compatibilizers may be copolymers in which acrylonitrile-styrene copolymer is grafted onto polycarbonate or copolymers in which polystyrene resin is grafted onto polycarbonate, with examples including Modipa C H430, L430D, and L150D manufactured by Nippon Yushi K.K. Moreover, polymethylmethacrylate (PMMA) may also be used as a compatibilizer. There are no particular restrictions on the amounts of these substances to be used, but they should preferably be added in amounts of 0.1 to 30 parts by weight with respect to a total of 100 parts by weight of components (A)+(B).
There are no particular restrictions on the method of manufacturing the resin composition of the present invention, and any common method may be satisfactorily used. Nevertheless, the melt mixing method is generally preferred. Small amounts of solvents may also be used, but these are generally unnecessary. Specific examples of devices which may be used include extruders, Banbury mixers, rollers, and kneaders. These devices may operate either by the batch method or continuously. Furthermore, there are no particular restrictions on the order of mixing of the components of the composition.